The present invention first relates to a front-lens attachment for an optical observation device according to the preamble of patent claim 1 as well as to the preamble of patent claim 7. In addition, the invention also relates to a turret attachment for the rotatable arrangement of at least two lens elements on a front-lens attachment for an optical observation device, an optical observation device as well as the special use of such a front-lens attachment or optical observation device.
Optical observation devices may involve, for example, microscopes, e.g., operating microscopes, in particular operating microscopes for ophthalmology, or the like. Such microscopes, among other things, usually have a microscope body with different optical elements and a tube piece. In addition, microscopes usually have at least one objective element. Not rarely, front-lens attachments are fastened in the region surrounding the objective element of the microscope.
Front-lens attachments for microscopes are already known in different embodiments. They usually serve for the purpose of introducing additional lens elements into a beam path of the microscope. A field of application for such front-lens attachments is the field of indirect ophthalmoscopy.
The retina or regions of the vitreous body of an eye can be imaged by means of an additional optical component in the form of at least one lens element, for example, a highly refractive single lens or group of lenses, which is positioned as defined, in front of the eye. The image of the back segment of the eye that is obtained in this way can be observed, if necessary, with appropriate observation devices, in particular with a stereoscopic operating microscope. Thus, the position of the image is dependent on the ophthalmoscopic magnifying lens used, particularly with respect to its refractive power, on the refractive error of the eye to be observed, e.g., near-sightedness or farsightedness, on the region/segment of the eye that is under observation, for example, the retina, regions of the vitreous body at a distance x over the retina or the like, on anomalies of the eye, for example, “liquid/oil-filled”, “gas-filled” natural vitreous body; phakic, “aphakic”, “pseudophakic” [intraocular lenses] and the like, on the distance between the ophthalmoscopic magnifying lens and the patient's eye, and similar dependencies.
By means of the front-lens attachment, the optical component is placed either directly onto the eye to be observed, for example, in the form of an indirect contact lens, or is held suspended at a certain distance in front of the eye to be observed, for example, by means of an indirect ophthalmoscopic magnifying lens in the “non-contact” region.
Depending on the optical properties of the ophthalmoscopic magnifying lens or of the contact lens, large, wide-angle regions of the fundus of the eye can be observed in this way, e.g., by magnifying lens or magnifying glasses with high refractive power, or, on the other hand, smaller regions of the fundus of the eye that are highly resolved can be observed by magnifying lens or magnifying glasses with lower refractive power. For an optimal or frame-filling image, each ophthalmoscopic magnifying lens or each contact lens shall be positioned at a specific distance from the eye, a distance that depends on the refractive power of the lens, since if it is not, vignetting due to the iris or similar effects may occur.
Different limiting conditions during a surgical operation, such as, for example, the fittings of the ophthalmoscopic magnifying lens, the accessibility and the working space in the vicinity of the eye of the patient, and similar conditions make it necessary, under certain circumstances, to move the ophthalmoscopic magnifying lens away from the eye, in particular, in the case of ophthalmoscopic magnifying lenses with very short focal lengths which usually must be positioned very closely to the eye. Because of this, the position of the (intermediate) image is shifted and this also leads to vignetting.
For example, such a front-lens attachment for a microscope is described in German Utility Model G 94 15 219 U1. The microscope involves an operating microscope for ophthalmology for observation of an eye. Among other things, the microscope has a principal objective, in the vicinity of which is attached the front-lens attachment. The known front-lens attachment has a holding or retaining device in the form of a retaining arm on which a lens element is disposed, which can be swung as desired into the beam path passing through the objective. For this purpose, the retaining arm is attached to a positioning device, which involves a rod assembly. First of all, the retaining arm, and with it the lens element, can be swung around the rod assembly. In addition, another linear drive is provided. The rod assembly can be moved via this linear drive in the lengthwise direction parallel to the optical axis. The retaining arm, and with it the lens element, can thus also be moved via the rod assembly in the lengthwise direction parallel to the optical axis, so that the position of the lens element can be moved on the optical axis between the objective and the eye to be observed. The positioning device is attached to the microscope via a fastening device, which is formed as an adapter in the known solution. The fastening device is designed in such a way that the entire front-lens attachment can be swung out of the beam path.
Whereas a front-lens attachment is described in G 94 15 219 U1 by which it is possible to introduce a single lens element as desired into the beam path, a front-lens attachment with a similar construction is described in U.S. Pat. No. 6,943,942 B, by which means it is also possible to introduce two lens elements selectively into the beam path. This known solution provides for the presence of two lens elements, each of which is attached via its own retaining device in the form of a retaining arm to a positioning device in the above-depicted manner. This known solution aims at being able to temporarily swing a second lens also into the beam path of the microscope, in order to manipulate the refractive power of the lens element in such a way that the front segment of the eye can be observed.
The previously known solutions, of course, have a number of disadvantages. Thus, for a known front-lens attachment, as is described, for example, in U.S. Pat. No. 5,793,524 B, a relatively large structural space is required, since a linear movement of the lens element must be conducted in the lengthwise direction and thus parallel to the optical axis. Focussing via a linear movement of the lens element relative to the observation device and thus to the eye of the patient represents great disadvantage. During focussing, the position of the pupil also changes simultaneously. If, for example, the position of the pupil of the observation device lies too far removed from the entrance pupil of the eye of the patient, there is an undesired vignetting, since the visible region of the fundus of the eye will become smaller. The alignment and focussing is thus an iterative process. Even if the lens element is swung out of the beam path, or is found in a position in the vicinity of the objective, the structural space cannot be reduced, since the positioning rod assembly and the linear drive remain unchanged in their lengthwise extension and positioning. The front-lens attachment in and of itself is also formed with a relatively large volume due to the linear drive. This also has various disadvantages. If, for example, the front-lens attachment is completely swung out horizontally, as this is described as being possible in G 94 15 219 U1, a considerable empty space is necessary, into which the front-lens attachment can be swung in. In addition, it is also difficult to clean the front-lens attachment and, if needed, to sterilize it. If microscopes are employed as operating microscopes, then front-lens attachments must be sterilized after use, which is usually carried out in an autoclave. Large, complex and bulky components can be sterilized only with great difficulty in an autoclave.
In addition, the known solutions are complex in their construction and are thus expensive, particularly since a separate drive must be maintained. Such drives, which for the most part function electrically can also be sensitive to interference.